The present invention relates to wireless digital networks, and in particular, to the problem of determining when a station is at the edge of wireless local area network (WLAN) coverage.
Wireless digital networks are becoming ubiquitous in enterprises, providing secure and cost-effective access to resources. Those networks usually have one or more controllers, each controller supporting a plurality of access points (AP) deployed through the enterprise. WiFi networks operating in accordance with IEEE 802.11 standards are examples of such networks.
Also increasing in popularity are dual-mode handsets, which are handsets supporting not only a cellular/wireless wide area network (WWAN) interface, for example, GSM, CDMA, 3G or 4G, but also a wireless interface such as IEEE 802.11 WiFi. Such dual-mode handsets when used with properly configured and operating wireless local area networks (WLANs) offer the use of WiFi connections while the handset is within the enterprise, and cellular connections while outside the enterprise.
Handover of voice calls and data sessions between cellular and WLAN networks is a key concern for handset users and the designers of the WLANs they use.
In order to aid the timely handover of calls and sessions from a WiFi network to a WWAN, it is important to recognize when a dual-mode handset that is using WiFi is approaching the edge of WLAN coverage and is at risk of losing that coverage so that the required signaling can be completed between the WLAN and the WWAN to transition calls and/or data sessions before WLAN coverage is completely lost.
Being on the edge of WLAN coverage is a property of a client associated to a WiFi network. A initial assessment of this property may be made by identifying those APs along the edge of the WLAN; clients associated to one of these edge APs are on the edge of the WLAN. But association with an edge AP is not sufficient. Two clients may be associated with the same edge AP and be in different states. As an example, one client may be moving away from the edge AP and into the interior of the network. The other client may be moving away from the edge AP and away from the WLAN network entirely.
What is needed is a way of better identifying client devices on the edge of WLAN coverage in the network.